The prospects for feeding humanity as we enter the new millennium are formidable. The progressive salinization of irrigated land compromises the future of agriculture in the most productive areas of our planet (Serrano et al., 1994). Arid regions offer optimal photoperiod and temperature conditions for the growth of most crops, but suboptimal rainfall. Artificial irrigation has solved the problem in the short term. However, water supplies always contain some dissolved salt, which upon evaporation gradually accumulates on the soils. To grow in saline environments, plants must maintain a much lower ratio of Na+/K+ in their cytoplasm than that present in the soil. Thus, a need exists for crops having increased tolerance to salt.
In worldwide agricultural production, phosphorus is second only to nitrogen as the most limiting macronutrient. In soils, orthophosphate (Pi), the assimilated form of phosphorus, exists primarily as insoluble calcium salts or iron-aluminium oxide complexes that are inaccessible to plants (Holford, 1997). When aggressive fertilization is employed to alleviate available Pi deficiency, runoff from agricultural land represents a serious threat to aquatic and marine environments (Hammond et al., 2004). Thus, a need exists for crops having increased Pi uptake.